JP4544823B2 - Out-of-plane operation method of thermal MEMS actuator and thermal MEMS actuator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an out-of-plane operation method and a thermal MEMS actuator for a thermal microelectromechanical system (MEMS) actuator, and more particularly, to an out-of-plane operation method and a thermal MEMS actuator for a thermal MEMS actuator driven by Joule heating. It relates to the structure of the actuator.
[0002]
[Prior art]
Microelectromechanical system (MEMS) actuators provide control of ultra-small components formed on a semiconductor substrate by conventional semiconductor (eg, CMOS) manufacturing processes. MEMS systems and MEMS actuators are sometimes referred to as micromachined systems-on-a-chip.
[0003]
One conventional MEMS actuator is an electrostatic actuator or a comb drive. In general, such an actuator includes two comb structures, each having a plurality of comb fingers aligned in a plane parallel to the substrate. The two comb teeth engage each other. The potential difference applied to the comb structure establishes an electrostatic interaction between the two comb structures, which causes the comb structures to move toward and away from each other.
[0004]
The advantage of electrostatic actuators is that less current is required, thereby lowering the operating energy and having a relatively high frequency response. The disadvantage of the electrostatic actuator is that it requires a high driving voltage (for example, tens or hundreds of volts) and a large area, and the output force is small. Comb drive (electrostatic) actuators used for microstructure placement typically occupy many times the area of the device being placed. Furthermore, the high voltage (eg, tens or hundreds of volts) required to operate the electrostatic actuator is incompatible with conventional logic and low voltage electronics and may hinder integration.
[0005]
  The pseudo bimorph thermal actuator is an alternative embodiment of an electrostatic actuator. This actuator uses a differential thermal expansion of two differently sized polysilicon arms to generate a pseudo bimorph that deforms in an arc parallel to the substrate. Such a thermal actuator has a much greater force generated per unit volume (100-400 times) than a comb drive actuator, and can operate at very low voltages. Such actuators are limited in sweep or arc motion in the plane of the actuator.
Several documents disclose the technical contents related to the conventional technique as described above (see, for example, Patent Documents 1 to 3).
[Patent Document 1]
European Patent No. 1201602
[Patent Document 2]
International Publication No. 00/67268 Pamphlet
[Patent Document 3]
European Patent No. 1143467
[0006]
[Problems to be solved by the invention]
The conventional MEMS actuator has various problems as described above, and further improvement is desired.
[0007]
The present invention has been made in view of such problems, and an object thereof is to provide an out-of-plane operation method of a thermal MEMS actuator driven by Joule heating capable of out-of-plane motion and a thermal MEMS actuator. There is.
[0008]
[Means for Solving the Problems]
The present invention includes an out-of-plane thermal buckle beam microelectromechanical actuator formed on a planar substrate of semiconductor material (eg, silicon). The actuator includes first and second anchors secured to the substrate and a plurality of elongated thermal buckle beams secured between the anchors. This buckle beam is formed of a semiconductor material such as polysilicon. In one implementation, each buckling beam has at least one pivot arm that includes a frame base fixed to each buckle beam and a free end that is coupled to the frame base and pivots out of plane when the actuator is driven. And is connected by a pivot frame including
[0009]
The periodic current source sends the periodic current through the anchor into the thermal buckle beam, resulting in thermal expansion of the buckle beam, and thus the periodic bending motion of the buckle beam out of the plane of the substrate (i.e. away from the substrate). Bring. In one implementation, the actuator has a natural resonant deflection frequency range, and the frequency of the periodic current is a first frequency within the resonant deflection frequency range.
[0010]
The actuator according to the present invention realizes out-of-plane motion with the same level of force as a conventional thermal actuator. The resistivity of silicon allows the actuator to operate at voltages and currents that are compatible with standard integrated circuits (eg, CMOS). In addition, the area of the actuator according to the invention is very small and has a relatively large force. This electrically induced motion can be used in micromotors, optical scanning devices, MEMS optical placement mechanisms, and other areas that require microscale mechanical motion. For example, the actuator structure of the present invention includes a pair of actuators or actuators that cross each other and an out-of-plane planar fold mirror that cooperate to form a video raster scanner.
[0011]
Further objects and advantages of the present invention will become apparent from the embodiments of the invention which will be described with reference to the accompanying drawings.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0013]
To assist in understanding the present invention, a general procedure for manufacturing micromechanical devices using the MUMPs process will be described with reference to FIGS.
[0014]
The MUMP process provides three layers of conformal polysilicon, and the three layers of conformal polysilicon are etched to create the desired physical structure. The first layer, called POLY0, is bonded to the support wafer, and the second and third layers, called POLY1 and POLY2, respectively, are mechanical layers. This mechanical layer can be separated from the underlying structure by using a sacrificial layer that separates the layers and is removed during the process.
[0015]
The attached figure shows the general process for building a micromotor provided by MEMS Technology Applications Center, 3021 Cornwallis Road, Research Triangle Park, North Carolina.
[0016]
The MUMP process starts with a 100 mm n-type silicon wafer 10. The wafer surface is heavily doped with phosphorus in a standard diffusion furnace using POCI 3 as a dopant source. This reduces charge penetration from the electrostatic device that is subsequently mounted on the wafer into the silicon. Next, a 600 nm LPCVD (Low Pressure Chemical Vapor Deposition) silicon nitride layer 12 is deposited on the silicon as an electrical isolation layer. The silicon wafer and the silicon nitride layer form a substrate.
[0017]
Next, a 500 nm LPCVD polysilicon coating POLY014 is deposited on the substrate. Next, the POLY0 layer 14 is patterned by photolithography. In this step, for the purpose of transferring the pattern to the POLY0 layer later, the POLY0 layer is covered with a photoresist 16, the photoresist is exposed with a mask (not shown), and the exposed photoresist is developed to obtain a desired pattern. Generating an etching mask (FIG. 2). After patterning the photoresist, the POLY0 layer 14 is etched with a reactive ion etching (RIE) system (FIG. 3).
[0018]
Referring to FIG. 4, a 2.0 μm phosphosilicate glass (PSG) sacrificial layer 18 is deposited on the POLY0 layer 14 and on the exposed portion of the nitride layer 12 by LPCVD. This PSG layer, referred to herein as the first oxide, is removed at the end of the process, and the first mechanical layer of polysilicon POLY1 (described below) is the underlying structure. That is, it is peeled off from POLY0 and the silicon nitride layer. The sacrificial layer is lithographically patterned using a DIMPLES mask, and a 750 nm deep recess 20 is formed in the first oxide layer by RIE (FIG. 5). The wafer is then patterned with a third mask layer ANCHOR1 and etched (FIG. 6), resulting in anchor holes 22 extending from the first oxide layer to the POLY0 layer. The hole of ANCHOR1 will be filled with POLY1 layer 24 in the next step.
[0019]
After the etching of ANCHOR1, a polysilicon first structural layer (POLY1) 24 is deposited to a thickness of 2.0 μm. A thin 200 nm PSG layer 26 is then deposited over the POLY1 layer 24, the wafer is annealed (FIG. 7), and the POLY1 layer is doped with phosphorus from the PSG layer. Annealing also reduces the stress in the POLY1 layer. The POLY1 layer and the PSG masking layers 24 and 26 are patterned by lithography to form the POLY1 layer structure. After etching the POLY1 layer (FIG. 8), the photoresist is removed and the remaining oxide mask is removed by RIE.
[0020]
After the POLY1 layer 24 is etched, a second PSG layer (hereinafter referred to as “Second Oxide”) 28 is deposited (FIG. 9). The second oxide is patterned using two different etch masks with different purposes.
[0021]
First, an etching hole reaching the POLY1 layer 24 is provided in the second oxide by POLY1_POLY2_VIA etching (denoted by 30). This etching provides a mechanical and electrical connection between the POLY1 layer and the subsequent POLY2 layer. The POLY1_POLY2_VIA layer is patterned by lithography and etched by RIE (FIG. 10).
[0022]
Second, an ANCHOR2 etch (shown at 32) is provided to etch both the first oxide layer 18 and the second oxide layer 28 and the POLY1 layer 24 in one step (FIG. 11). In the ANCHOR2 etching, as in the POLY1_POLY2_VIA etching, the second oxide layer is patterned by lithography and etched by RIE. FIG. 11 shows a wafer cross-sectional view after both the POLY1_POLY2_VIA etching and the ANCHOR2 etching are completed.
[0023]
A second structural layer POLY2 34 is then deposited with a thickness of 1.5 μm, followed by a PSG of 200 nm. The wafer is then annealed and the POLY2 layer is doped to reduce its residual film stress. Next, the POLY2 layer is patterned by lithography using a seventh mask, and the PSG and POLY2 layers are etched by RIE. The photoresist can then be stripped and the masking oxide is removed (FIG. 13).
[0024]
The final deposited layer in the MUMP process is a 0.5 μm metal layer 36 that provides probing, bonding, and electrical routing and provides a high reflectivity mirror surface. The wafer is lithographically patterned using an eighth mask, and metal is deposited and patterned using a lift-off technique. The final unstretched exemplary structure is shown in FIG.
[0025]
Finally, the sacrificial layer is stripped and tested using known methods. FIG. 15 shows the device after the sacrificial oxide is stripped.
[0026]
In a preferred embodiment, the device of the present invention is manufactured according to the steps described above by a MUMP process. However, the device of the present invention does not use the specific mask pattern illustrated in the general process of FIGS. 1-15, but uses a mask pattern specific to the structure of the present invention. Further, the above steps for the MUMP process may be modified as directed by the MEMS Technology Applications Center. The manufacturing process is not part of the present invention, but only one of several processes that can be used to create the present invention.
[0027]
FIG. 16 is a plan view of a microelectromechanical out-of-plane thermal buckle beam actuator 50 according to the present invention. Actuator 50 is secured to anchors 52 and 54 with a pair of structural anchors 52 and 54 secured to a substrate (e.g., not shown, substrate 10 and nitride layer 12) and base ends 60 and 62, respectively. One or more thermal buckle beams 56 (multiple thermal buckle beams shown). Each buckle beam 56 is substantially the same, extends substantially parallel to the substrate, is spaced from the substrate, and except for the anchors 52 and 54 are peeled away from the substrate.
[0028]
The pivot frame 64 includes a frame base 66 that is secured to the buckle beam 56 at a connection point 68. In one implementation, the coupling point 68 is located between the mid-point of the buckle beam (shown by the dashed line 70) and one of the anchors 52 and 54 (eg, anchor 54). The pivot frame 64 further includes at least one pivot arm 72 (two pivot arms are shown). The pivot arm 72 is coupled to the frame base 66 at one end and extends to a free end 74 that pivots out of plane when the actuator 50 is driven. The pivot frame 64 is peeled and moved freely except where the frame base 66 is fixed to the coupling point 68. FIG. 17 is a side view of the actuator 50 in a relaxed state, showing the pivot frame 64 as being generally parallel to or coplanar with the buckle beam 56.
[0029]
The structural anchors 52 and 54 and the buckle beam 56 are semiconductive and have a positive coefficient of thermal expansion characteristic. For example, the buckle beam 56 is formed of silicon.
Actuator 50 is driven from current source 80 as current passes through buckle beam 56 through conductive couplings 82 and 84 and structural anchors 52 and 54, respectively. The applied current induces ohmic or joule heating of the buckle beam 56, which causes the buckle beam 56 to expand longitudinally due to the positive thermal expansion coefficient of silicon. The anchors 52 and 54 that restrain the base ends 60 and 62 of the buckle beam 56 ultimately cause the buckle beam 56 to bend away from the substrate. In one implementation, the buckle beam 56 has a wide aspect ratio where the width (parallel to the substrate) is greater than the thickness (perpendicular to the substrate) so that it is biased or prone to not bend parallel to the substrate. It is formed. For example, the buckle beam 56 has a width of 3 μm, a thickness of 2 μm, a length of 194 μm, and a wide cross-sectional aspect ratio of 3: 2. FIG. 18 is a side view of the actuator 50 in the driving state showing the out-of-plane curvature of the buckle beam 56.
[0030]
In the active state of the actuator 50, the curvature of the buckle beam 56 away from the substrate causes the free end 74 of the pivot frame 64 to pivot away from the substrate. The pivot frame 64 rotates about the frame base 66 and the frame base 66 is also lifted from the substrate by the buckle beam 56. As a result, the free end 74 moves and exerts a turning force or a rotational force toward the outside of the substrate. When the drive current stops, the buckle beam 56 cools and contracts, thereby returning the free end 74 of the pivot frame 64 to its initial position. Such rotational deflection of the pivot frame 64 can be used in a variety of applications, including the realization of out-of-plane placement of other micromechanical structures such as those used in micro-optical devices. In the implementation shown in FIGS. 16-18, for example, the mirror 86 is fixed to the free end 74 and pivots with the pivot frame 64 so that light is selectively selected according to whether the actuator 50 is in its relaxed or driven state. Deflected.
[0031]
The wide aspect ratio of the buckle beam 56 generally prevents the buckle beam 56 from bending parallel to the substrate. If there is no bias or tendency, the curvature of the buckle beam 56 perpendicular to the substrate (eg, FIG. 18) can optionally occur in a direction away from or toward the substrate. The operation of the actuator 50 requires a curve away from the substrate. Accordingly, FIGS. 19 and 20 illustrate a biasing structure that provides a biasing or trending for the buckle beam 56 to curve away from the substrate, not in the direction toward the substrate.
[0032]
  FIG. 19 is an enlarged view showing an exemplary buckle beam 56 in a relaxed state that is secured to the substrate 10 and extends from the substrate 10 (eg, the nitride layer 12) and extends above the spacing pad 90 near the center of the buckle beam 56. It is a side view. The pivot frame is not shown for ease of illustration. FIG. 20 is an enlarged side view showing an exemplary buckle beam 56 in the driven state. For example, the spacing pad 90 can be formed with a 0.5 μm thick P0 layer and the buckle beam 56 can be formed with a different (peeling) layer. Spacing pad 90 pushes out a small (eg, 0.5 μm) hump or deflection 94 within each buckle beam 56 due to the conformal nature of the fabrication. In addition, a recess 92 is formed near each end of the buckle beam 56. As shown, the recess 92 may be formed as a protrusion or recess extending from the bottom surface of the buckle beam 56, or as a recess in the top surface of the buckle beam 56, or both. In the implementation of MUMP, for example, 2umPOLYAs a 0.5 um depression in one layer, the depression 92 can be formed so as not to touch the substrate.
[0033]
Spacing pad 90 and indentation 92 cause buckle beam 56 to bend away from the substrate, reducing the stiction between buckle beam 56 and the substrate (eg, nitride layer 12). For multiple buckle beams 56 within a typical actuator 50, a separate spacing pad 90 can be formed for each buckle beam 56, or the spacing pad 90 can be a single extension that extends under all the buckle beams 56. It will be understood that it can be formed as a continuous pad of The spacing pad 90 and the indentation 92 are used individually or together and used alone or in conjunction with a wide aspect ratio for the buckle beam 56 such that the buckle beam 56 bends away from the substrate. A trend can be realized.
[0034]
Initial experiments have demonstrated that the actuator 50 can achieve pivoting or deflection of the pivot frame 64 at least about 15 degrees relative to the substrate. In one implementation, maximum pivoting or deflection of the pivot frame 64 is obtained by securing the frame base 66 to a midpoint of coupling 68 between the midpoint of the buckle beam and one of the anchors 52 and 54. Such a coupling point 68 corresponds to an inflection point in the beam 56 when the beam 56 is curved, thus providing maximum deflection of the pivot frame 64.
[0035]
In general, the present invention is adaptable to any manufacturing process that includes a positive temperature expansion coefficient and includes at least one peelable layer capable of carrying a current for ohmic heating. Further, there is no theoretical limit on the number of buckle beams 56 as long as the actuator and its associated conductor can handle the current and heat and the beam can quickly lose heat. In one implementation, the heating temperature was kept below 800 ° C. to prevent self-annealing that could cause irreversible damage.
[0036]
  Buckle beam 56 and anchors 52 and 54One or both ofPeelable MUMP polysiliconLayerThe anchors 52 and 54 do not peel off. In such a MUMP implementation, the actuator 50 can have a possible thickness of 1.5, 2.0, or 3.5 μm. The resistivity of polysilicon allows the actuator to operate at voltages and currents that are compatible with standard integrated circuits (eg, CMOS). In addition, the area of the actuator according to the invention is very small and has a relatively large force.
[0037]
In one mode of operation, the mirror 86 and the pivot frame 64 can form a pendulum that oscillates around the frame base 66, thereby allowing the actuator 50 to operate as a resonant oscillator. In one implementation, such a resonant mode occurs at 14 kHz, resulting in a peak deflection of the mirror 86 of about 25 degrees relative to the relaxed state. In this mode, the buckle beam 56 appears to exhibit a near steady state deflection position, resulting in a static deflection of the mirror 86 and pivot frame 64. On the other hand, in the non-resonant mode of this implementation, the actuator 50 has a half amplitude response of about 2 kHz and a deflection of about 5 degrees.
[0038]
FIG. 21 is a graph 150 showing the upper and lower limits of angular deflection as a function of frequency to illustrate the resonant operation of the actuator 50 of the present invention. In this figure, the actuator 50 is excited with a 4 volt square wave. Graph 150 shows the half amplitude bandwidth (data point 152) at about 1 kHz and resonant actuator deflection at about 8 kHz (data point 154). In this implementation, the resonant actuator deflection (eg, mirror 86) has a maximum total displacement 18 for optical degree (ie, out-of-plane).
[0039]
Resonant actuator deflection occurs within a resonant deflection frequency range 156 that follows the frequency range of reduced angle deflection. The resonant deflection frequency range 156 can be further characterized by an increase (or decrease) in angular deflection with a greater slope.
[0040]
Note that at frequencies above the resonant frequency (ie, about 8 kHz), the periodic actuator deflection decreases rapidly until it exhibits a static deflection value (data point 158). In this state, it is considered that the actuator 50 cannot mechanically respond to the rapid heating and quenching of the buckle beam 56. The static deflection value is equal to the static residual stress offset of 4.5 degrees (data point 160) plus the deflection due to the RMS heating value of 2 volts for the applied square wave, and a total offset of 10 degrees at data point 158. Is obtained. The bias due to the residual stress and the average heating value of the drive signal contributes to lifting the mirror 86 upward and avoiding collision with the substrate.
[0041]
FIG. 22 illustrates a microelectromechanical out-of-plane buckle beam actuator comprising a plurality (eg, two) of actuators 102A, 102B that are aligned with adjacent sides of a rectangular (eg, square) mirror 120 and are disposed orthogonal to each other. 2 is a plan view of an exemplary implementation of assembly 100. FIG. The actuators 102A, 102B are similar to the actuator 50 described above, except that each includes a pivot frame 110A, 110B that is different from the pivot frame 64. Similarly, mirror 120 is similar to mirror 86, but is differently attached and coupled to pivot frames 110A, 110B. The following description is directed to the actuator 102A, but is similarly applicable to the actuator 102B. Similar components of actuator 102A and actuator 102B are indicated by the same reference numerals.
[0042]
Actuator 102A includes a pair of structural anchors 52A and 54A secured to a substrate (eg, substrate 10 or nitride layer 12 not shown) and a plurality of thermal buckles secured to anchors 52A and 54A at the base end. Beam 56A. The pivot frame 110A has a frame base 112A fixed to the buckle beam 56A and one pivot arm 114A that is coupled to the frame base 112A at one end and extends to a free end 116A that pivots out of plane when the actuator 102A is driven. Including. The free end 116A is attached to one corner of the mirror 120, which is linked to the mirror anchor 124 by a tendon 122 or peeled off the substrate.
[0043]
Actuator 102A is driven when current passes through buckle beam 56A from current source 124A through conductive couplings 126A and 128A and structural anchors 52A and 54A, respectively. As before, the applied current induces ohmic or joule heating of the buckle beam 56A, which causes the buckle beam 56A to expand in the longitudinal direction due to the positive thermal expansion coefficient of silicon.
[0044]
Actuators 102A and 102B serve to tilt mirror 120 about tilt axes 130A and 130B, respectively. Actuators 102A and 102B, each having current sources 124A and 124B, can be operated separately to arbitrarily tilt mirror 120 about tilt axes 130A and 130B. By adjusting the operation, the actuator assembly 100 and mirror 120 can be used as a scan control mirror in a barcode scanner or vector image scanner, or can be used to provide a raster scan pattern for image formation. it can.
[0045]
FIG. 23 is a plan view of a pair of microelectromechanical out-of-plane thermal buckle beam actuators 50H and 50V, both configured to function as part of video raster scanner 200 (FIGS. 24 and 27). Actuators 50H and 50V have substantially the same configuration as actuator 50 of FIG. 16, and thus corresponding similar components have the same reference numerals. For example, actuators 50H and 50V include mirrors 86H and 86V, respectively.
[0046]
As will be described in more detail below, actuators 50H and 50V comprising mirrors 86H and 86V function to achieve horizontal and vertical scanning of image display light beam 202 (FIG. 24) from display light source 204, respectively. . High frequency horizontal scanning is realized by the actuator 50H, and low frequency vertical scanning is realized by the actuator 50V. For example, in the NTSC standard display format, horizontal scanning at a frequency of about 15 kHz is realized by the actuator 50H, and scanning at a frequency of about 60 Hz is realized by the actuator 50V. Thus, the actuator 50H can be configured with a resonant deflection frequency range 156 that includes an operating frequency of nominally 15 kHz. The display light source 204 may be any monochromatic or multicolor focused or parallel light source that is modulated on a pixel-by-pixel basis.
[0047]
FIG. 24 is a side view showing the operation of actuators 50H and 50V with light source 204 and generally stationary fold mirror 206. FIG. Actuators 50H and 50V, along with fold mirror 206, are formed on a common substrate 208 (shown) or are formed on separate substrates that are generally coplanar. In FIG. 24, actuators 50H and 50V oscillate out of the plane of substrate 208 about horizontal axes (eg, vertical axis shown) 210 and 212, respectively. The light beam 202 from the light source 204 reflects from the mirror 86H to the fold mirror 206 as a light beam segment 202A, and then reflects from the fold mirror 206 to the mirror 86V as a light beam segment 202B.
[0048]
25 and 26 are a plan view and a side view of the fold mirror 206, respectively. Each of them is shown alone for easy viewing. The fold mirror 206 is formed on a body 220 that is inclined or curved with respect to the substrate 208. Aperture 222 (shown schematically in FIG. 24) extends through body 220 and allows light from light source 204 to pass through body 220 and to mirror 86H of actuator 50H.
[0049]
The body 220 is formed as one or more semiconductor layers according to the semiconductor manufacturing process used to manufacture the actuators 50H and 50V. Thus, fold mirror 206 may simply be the surface of a semiconductor material. In addition, the body 220 includes a main surface region 224 on which the material layer (eg, gold) has an expansion coefficient that is different from the expansion coefficient of the semiconductor material of the body 220.
[0050]
  The difference between the expansion coefficient of the body 220 and the expansion coefficient of the layers in the region 224 induces a residual stress during manufacturing, and the residual stress causes the body 220 to be tilted or curved out of the plane of the substrate 208. In one implementation, the body 220 includes an end region 226 formed as a reinforced multilayer structure, therebyedgeResidual stress problems are prevented from forming in region 226. By aligning end region 226 with mirror 206, end region 226 allows body 220 and fold mirror 206 to remain generally flat. As a result, the mirror 206 can more accurately reflect the light from the mirror 86H of the actuator 50H to the mirror 86V of the actuator 50V.
[0051]
FIG. 27 is a plan view of the video raster scanner 200 showing the body 220 that supports the fold mirror 206 disposed on the actuator 50H. The light source 204 (FIG. 24) directs the light beam 202 through the aperture 222 to the mirror 86H of the actuator 50H.
[0052]
FIGS. 28A-28D show a schematic representation of one implementation of successive steps in manufacturing and operating the video raster scanner 200. FIG. 28A shows an initial manufacturing layout 250 of actuators 50H and 50V for folding mirror body 220. FIG. It should be understood that in initial manufacture, the actuators 50H and 50V and the folding mirror body 220 are formed in the plane of the substrate 208.
[0053]
FIGS. 28B and 28C show manufacturing layouts 252 and 254 after initial manufacturing layout 250, respectively. Manufacturing layouts 252 and 254 show that folding mirror body 220 moves along at least one pair of guides 256 to an intermediate manufacturing position and a final manufacturing position, respectively. The guide 256 is fixed to the substrate 208, extends from the substrate 208, and extends on the side margin of the body 220. The body 220 is slidable with respect to the substrate 208 and the guide 256.
[0054]
In one implementation, the guide 256 is formed in the longitudinal direction of the body 220 in the initial manufacturing layout 250. As the body 220 moves from the initial manufacturing position (layout 250) to the intermediate and final manufacturing positions (layouts 252 and 254), one after another, more regions 224 extend beyond the guides 256 and the residual stress in the region 224 is increased. Accordingly, the body 220 is inclined or curved in a direction away from the substrate 208. It will be appreciated that the body 220 can be moved from its initial manufacturing position to its final manufacturing position by automatic (ie, actuator) control or manual operator operation as is well known in the art. FIG. 28D is a plan view showing the operation of the video raster scanner 200.
[0055]
Note that mirrors 86H, 86V, and 206 must be made large enough to accommodate the range of movement of light beam 202 relative to the individual moving mirrors and the movement of light beam segments 202A and 202B.
[0056]
In part of the description of the preferred embodiment, reference is made to the aforementioned MUMP manufacturing process steps. However, as mentioned above, MUMP is a common manufacturing process that addresses a wide range of MEMS device designs. Thus, a manufacturing process specifically designed for the present invention can include different steps, additional steps, different dimensions and thicknesses, and different materials. Such specific manufacturing processes are within the knowledge of those skilled in the art of photolithography processes and are not part of the present invention.
[0057]
In view of the many possible embodiments to which the principles of the present invention may be applied, it is to be understood that the detailed embodiments are merely examples and are not to be construed as limiting the scope of the invention. Rather, all embodiments that come within the scope and spirit of the following claims and their equivalents are claimed as inventions.
[0058]
【The invention's effect】
As described above, according to the present invention, a thermal MEMS actuator driven by Joule heating capable of out-of-plane motion can be provided.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a general multi-user MEMS process well known in the prior art for fabricating microelectromechanical devices, with cross-hatching omitted so that the illustrated prior art structure and process can be easily seen. is there.
FIG. 2 is a cross-sectional view of a general multi-user MEMS process known in the prior art for fabricating microelectromechanical devices, with cross-hatching omitted so that the illustrated prior art structure and process can be easily seen. is there.
FIG. 3 is a cross-sectional view of a general multi-user MEMS process known in the prior art for fabricating a microelectromechanical device, with cross-hatching omitted so that the prior art structure and process shown can be easily seen. is there.
FIG. 4 is a cross-sectional view of a general multi-user MEMS process known in the prior art for fabricating microelectromechanical devices, with cross-hatching omitted so that the illustrated prior art structure and process can be easily seen. is there.
FIG. 5 is a cross-sectional view of a general multi-user MEMS process known in the prior art for fabricating microelectromechanical devices, with cross-hatching omitted so that the illustrated prior art structure and process can be easily seen. is there.
FIG. 6 is a cross-sectional view of a general multi-user MEMS process well known in the prior art for fabricating microelectromechanical devices, with cross-hatching omitted so that the illustrated prior art structure and process can be easily seen. is there.
FIG. 7 is a cross-sectional view of a general multi-user MEMS process known in the prior art for fabricating microelectromechanical devices, with cross-hatching omitted so that the illustrated prior art structure and process can be easily seen. is there.
FIG. 8 is a cross-sectional view of a general multi-user MEMS process known in the prior art for fabricating microelectromechanical devices, with cross-hatching omitted so that the illustrated prior art structure and process can be easily seen. is there.
FIG. 9 is a cross-sectional view of a general multi-user MEMS process known in the prior art for fabricating microelectromechanical devices, with cross-hatching omitted so that the illustrated prior art structure and process can be easily seen. is there.
FIG. 10 is a cross-sectional view of a general multi-user MEMS process known in the prior art for fabricating microelectromechanical devices, with cross-hatching omitted so that the illustrated prior art structure and process can be easily seen. is there.
FIG. 11 is a cross-sectional view of a general multi-user MEMS process known in the prior art for fabricating microelectromechanical devices, with cross-hatching omitted so that the illustrated prior art structure and process can be easily seen. is there.
FIG. 12 is a cross-sectional view of a general multi-user MEMS process known in the prior art for fabricating microelectromechanical devices, with cross-hatching omitted so that the illustrated prior art structure and process can be seen easily. is there.
FIG. 13 is a cross-sectional view of a general multi-user MEMS process known in the prior art for fabricating a microelectromechanical device, with cross-hatching omitted so that the prior art structure and process shown can be easily seen. is there.
FIG. 14 is a cross-sectional view of a general multi-user MEMS process known in the prior art for fabricating microelectromechanical devices, with cross-hatching omitted so that the illustrated prior art structure and process can be easily seen. is there.
FIG. 15 is a cross-sectional view of a general multi-user MEMS process well known in the prior art for fabricating microelectromechanical devices, with cross-hatching omitted so that the illustrated prior art structure and process can be easily seen. is there.
FIG. 16 is a plan view of a microelectromechanical out-of-plane thermal buckle beam actuator according to the present invention.
17 is a side view of the actuator of FIG. 16 in a relaxed state.
18 is a side view of the actuator in FIG. 16 in a driving state.
FIG. 19 is an enlarged side view showing a buckle beam in a relaxed state having a bias structure that realizes a bias or tendency that the buckle beam curves away from the substrate.
FIG. 20 is an enlarged side view showing an activated buckle beam having a biasing structure that provides a biasing or tendency for the buckle beam to curve away from the substrate.
FIG. 21 is a graph showing the upper and lower limits of angular deflection as a function of frequency to illustrate the resonant operation of the actuator of the present invention.
FIG. 22 is a plan view of an exemplary implementation of a microelectromechanical out-of-plane buckle beam actuator assembly comprising a plurality of actuators.
FIG. 23 is a plan view of a pair of microelectromechanical out-of-plane thermal buckle beam actuators that are both configured to function as part of a video raster scanner.
24 is a side view showing the operation of the actuator of FIG. 23 as a video raster scanner.
25 is a plan view of a fold mirror used in the video raster scanner of FIG. 24. FIG.
26 is a side view of a fold mirror used in the video raster scanner of FIG. 24. FIG.
27 is a plan view of the video raster scanner of FIG. 24. FIG.
28A is a schematic diagram of one implementation of successive steps in manufacturing and operating the video raster scanner of FIGS. 24 and 27. FIG.
FIG. 28B is a schematic illustration of one implementation of successive steps in manufacturing and operating the video raster scanner of FIGS. 24 and 27.
FIG. 28C is a schematic illustration of one implementation of successive steps in manufacturing and operating the video raster scanner of FIGS. 24 and 27.
FIG. 28D is a schematic diagram of one implementation of successive steps in manufacturing and operating the video raster scanner of FIGS. 24 and 27.
[Explanation of symbols]
10 Silicon wafer
12 Silicon nitride layer, nitride layer
14 LPCVD polysilicon film POLY0, POLY0 layer
16 photoresist
18 Sacrificial layer, first oxide layer
20 Recess
22 Anchor hole
24 POLY 1 layer, first structure layer of polysilicon, PSG masking layer
26 PSG masking layer, PSG layer
28 Second PSG layer, second oxide layer
30 POLY1_POLY2_VIA etching
32 ANCHOR2 etching
34 Second structural layer POLY2
36 metal layers
50, 50H, 50V microelectromechanical out-of-plane thermal buckle beam actuator
52, 52A, 54, 54A Structure anchor
56, 56A Thermal buckle beam
60, 62 Base end
64 Pivot frame
66 frame base
68 attachment points
70 pivot arm
74 Free end
80 Current source
82 Conductive bond
84 Conductive bond
86, 86H, 86V Mirror
90 Spacing pad
92 Recess
94 Hump or deflection
102A, 102B Actuator
110A, 110B Pivot frame
112A frame base
114A pivot arm
116A free end
120 mirror
122 Tendon
124 Mirror Anchor
124A, 124B Current source
126A, 128A conductive coupling
200 video raster scanner
202 Image display light beam
202A, 202B Light beam segment
204 Display light source
206 Fold mirror
208 Common substrate
220 body
222 Aperture
224 Main surface area
226 End region
256 Guide

Claims (34)

Thermal microelectromechanical systems (MEMS) A work dynamic method of the actuator,
Opposite the planar substrate in the center of one or more elongated thermal buckle beams each having a first end and a second end secured to a first anchor and a second anchor coupled to the planar substrate. The thermal buckle beam is curved in a direction away from the flat substrate by forming a concave convex on the side and a recess not touching the flat substrate on the flat substrate side at the first and second ends. Step to
Sending an electric current through the anchor into the thermal buckle beam, which causes thermal expansion of the thermal buckle beam and movement of the thermal buckle beam in a direction away from the planar substrate, thereby causing the actuator work dynamic method of thermal MEMS actuators, characterized in that a step of driving. The actuator further includes a pivot frame including a frame base fixed to each buckle beam, and at least one pivot arm fixed to the frame base at one end and including a free end. The method of operating a thermal MEMS actuator according to claim 1, wherein the free end is pivoted in a direction away from the planar substrate . Wherein said step of curving the buckle beam has a wide aspect ratio, each buckle beam has a vertical thickness on the planar substrate and the width parallel to said planar substrate, and wherein the width of each buckle beam 2. The method of operating a thermal MEMS actuator according to claim 1, further comprising: being greater than a thickness of each buckle beam. Step, create the dynamic method of thermal MEMS actuator according to claim 1, wherein the actuator comprises a spacing pad extending under each buckle beam from the planar substrate to the curved. 2. The thermal MEMS of claim 1, wherein sending current into the thermal buckle beam includes sending a time-varying current into the thermal buckle beam to achieve a time-varying drive of the actuator. create dynamic method of the actuator. The change with time current is periodic, work dynamic method of thermal MEMS actuator according to claim 5, characterized in that to realize a periodic driving of the actuator. The frequency of the time-varying current is a first frequency, the time-varying current realizes periodic driving of the actuator with a first range of deflection, and the deflection of the first range is the first frequency. work dynamic method of thermal MEMS actuator according to claim 5, wherein the greater than the deflection of the second range to be achieved at a lower second frequency aging current than the frequency. Wherein the actuator has a natural resonant deflection frequency range, the frequency of the aging current work dynamic thermal MEMS actuator according to claim 6, wherein the a first frequency within the resonant deflection frequency range Method. Wherein the actuator has a natural resonant deflection frequency, said first frequency is created dynamic method of thermal MEMS actuators according to claim 8 wherein said is the same as the resonant deflection frequency. 3. The thermal MEMS of claim 2, wherein sending current into the thermal buckle beam includes sending a time-varying current into the thermal buckle beam to achieve a time-varying drive of the actuator. create dynamic method of the actuator. The change with time current is periodic, work dynamic method of thermal MEMS actuator according to claim 10, characterized in that to realize a periodic driving of the actuator. The frequency of the time-varying current is a first frequency, the time-varying current realizes periodic driving of the actuator with a first range of deflection, and the deflection of the first range is the first frequency. work dynamic method of thermal MEMS actuator according to claim 10, wherein greater than the deflection of the second range to be achieved at a lower second frequency aging current than the frequency. The frequency of the aging current work dynamic method of thermal MEMS actuator according to claim 10, characterized in that a first frequency within the resonant deflection frequency range. Wherein the actuator has a natural resonant deflection frequency, wherein the first frequency is created dynamic method of thermal MEMS actuator according to claim 13, wherein the is the same as the resonant deflection frequency. A first anchor and a second anchor fixed to the planar substrate;
One or more elongated thermal buckle beams each having a first end and a second end fixed to the first anchor and the second anchor, respectively , in the center of the thermal buckle beam; a buckle beam curved plane opposite to the substrate side in a direction away the first and second end portions and recesses of the projections from the planar substrate including a recess said not to touch the planar substrate side to the planar substrate of the convex,
A periodic current sent through the anchor into the thermal buckle beam, which causes thermal expansion of the thermal buckle beam and movement of the thermal buckle beam in a direction away from the planar substrate, thereby the actuator A thermal microelectromechanical system (MEMS) actuator characterized by comprising: a periodic current that realizes periodic driving. A pivot including a frame base fixed to each buckle beam and at least one pivot arm fixed at one end to the frame base and including a free end that pivots away from the planar substrate when the actuator is driven. The thermal MEMS actuator of claim 15, further comprising a frame.   The frequency of the periodic current is a first frequency, and the periodic current realizes periodic driving of the actuator with a deflection in a first range, and the deflection in the first range is greater than the first frequency. 17. The thermal MEMS actuator of claim 16, wherein the thermal MEMS actuator is greater than a second range of deflection realized with a periodic current of a lower second frequency.   The thermal MEMS actuator according to claim 16, wherein the actuator has a natural resonance deflection frequency range, and the frequency of the periodic current is a first frequency within the resonance deflection frequency range. Wherein the actuator has a natural resonant deflection frequency, the frequency of the periodic current, thermal MEMS actuator according to claim 16, wherein the a resonant deflection frequency and the same first frequency. A thermal microelectromechanical system (MEMS) actuator structure formed on a planar substrate,
A first bus Tsu Kuru beam actuator and the second bus Tsu Kuru beam actuators oriented in a direction crossing each other in the planar substrate,
A first anchor fixed to the planar substrate and a first end and a second end fixed to the second anchor; a concave indented on the opposite side of the planar substrate in the center; a plurality of elongated heat buckle beams having a recess without touching the planar substrate convex on one and the planar substrate side to the second end,
A pivot frame including a frame base fixed to a buckle beam and at least one pivot arm coupled to the frame base at one end and including a free end, the free end including a light reflector; and A pivot frame that pivots away from the planar substrate when the actuator is driven;
An electric current is sent through the anchor into the thermal buckle beam, causing thermal expansion of the thermal buckle beam and movement of the thermal buckle beam in a direction away from the planar substrate, thereby driving each actuator. comprising a first bar Tsu Kuru beam actuator and the second bus Tsu Kuru beam actuator having an electrical coupling, respectively,
Wherein mounted on the planar substrate, wherein the first further comprise an actuator and one flat surface fold mirror that will be held on the body located on the second actuator, the fold mirror through it, the first Aligned to reflect light between the light reflector of an actuator and a second actuator, the body allows light to propagate to the light reflector, or light propagates from the light reflector A structure of a thermal MEMS actuator comprising an aperture that can be made.   21. The thermal MEMS actuator structure of claim 20, further comprising periodic driving of the first and second actuators.   21. The thermal MEMS actuator structure of claim 20, further comprising periodic driving of the first actuator and the second actuator at different respective first and second frequencies.   The first actuator and the second actuator are further periodically driven, and at least one of the first actuator and the second actuator has a natural resonance deflection frequency range, and the first actuator and the second actuator The structure of the thermal MEMS actuator according to claim 22, wherein the frequency of the periodic drive of the at least one of the two actuators is a frequency within the resonance deflection frequency range.   21. The thermal MEMS actuator structure of claim 20, wherein the first actuator and the second actuator are generally orthogonal to each other.   25. The thermal MEMS actuator structure of claim 24, further comprising periodic driving of the first and second actuators at different first and second frequencies, respectively.   26. The thermal MEMS actuator structure of claim 25, wherein the first actuator and the second actuator cooperate to form a raster scan of the light beam. The periodic drive first and second frequencies, the structure of the heat MEMS actuator according to claim 26, characterized in that the horizontal television scanning frequency and vertical television scan frequencies of the NTSC standard. A first anchor and a second anchor fixed to the planar substrate;
One or more elongate thermal buckle beams each having a first end and a second end fixed to a first anchor and a second anchor, respectively, in the center and opposite to the planar substrate heat buckle beam curved away to the first and second end portions and recesses of the projections from the planar substrate including a recess said not to touch the planar substrate side to the planar substrate of the convex,
A pivot frame comprising: a frame base fixed to each buckle beam; and at least one pivot arm fixed to the frame base at one end and including a free end that bends away from the planar substrate when the actuator is driven. When,
A thermal microelectromechanical system (MEMS) actuator comprising: a natural resonance deflection frequency range in which a periodic deflection of the free end of the pivot arm receives a resonance deflection. A periodic current is sent through the anchor into the thermal buckle beam, resulting in thermal expansion of the thermal buckle beam and movement of the thermal buckle beam in a direction away from the planar substrate, thereby causing the actuator The thermal MEMS actuator according to claim 28, wherein the periodic driving is realized.   30. The thermal MEMS actuator according to claim 29, wherein the frequency of the periodic current is a first frequency within the resonance deflection frequency range. Wherein the actuator has a natural resonant deflection frequency, the frequency of the periodic current, thermal MEMS actuator according to claim 29, wherein said a first frequency the same as the resonant deflection frequency. Undergo periodic deflections in response to the periodic drive thermal buckle beams, are secured to the planar substrate at one end, and a thermal microelectromechanical system (MEMS) actuator having a pivot arm including a free end,
A natural resonance deflection frequency range in which the periodic deflection of the pivot arm receives a resonance deflection; and
It said end portion is secured to the planar substrate, coupled to said pivot arm, in order to deflect the pivot arm in a direction away from the planar substrate in response to the periodic drive of the pivot arm, the plane at the center one or more elongated the heat buckle beams curved in a direction away from the planar substrate including a recess and depressions convex side opposite to the substrate side not touch the planar substrate is convex on the plane side provided on the end portions And the periodic driving includes passing a periodic current through the thermal buckle beam to effect thermal expansion of the thermal buckle beam and movement of the thermal buckle beam in a direction away from the planar substrate. The thermal MEMS actuator characterized by the above-mentioned. The thermal MEMS actuator according to claim 32, wherein a frequency of the periodic current is a first frequency within the resonance deflection frequency range . 33. The thermal MEMS actuator of claim 32 , wherein the actuator has a natural f resonant deflection frequency, and the frequency of the periodic current is a first frequency that is the same as the resonant deflection frequency .

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